why does python ignore variables i import when pygame is running

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Summary

A variable imported with from cityMap import * appeared in autocomplete but failed at runtime because the module executed before the Pygame environment was ready, and because wildcard imports hide ordering problems. The variable gray was never actually available in the namespace you expected, even though the editor suggested it.

Root Cause

The failure comes from a combination of Python import semantics and Pygame side effects:

  • *Wildcard imports (`import `) copy names, not live references**
  • Modules execute immediately on import, including any top‑level Pygame calls
  • city.py references screen during import, but screen only exists in main.py
  • Because city.py crashes or partially loads, its variables never finish defining
  • Autocomplete shows symbols from static analysis, not from runtime execution

Why This Happens in Real Systems

Real Python systems often hit this because:

  • Import order matters, and circular imports silently break initialization
  • Pygame objects (like screen) must be created after pygame.init()
  • Top‑level code in modules is dangerous when it depends on external state
  • Wildcard imports hide where variables come from, making debugging harder

Real-World Impact

This pattern causes:

  • Partially imported modules, where some variables never get defined
  • Silent failures when top‑level code runs too early
  • Circular import loops that prevent modules from finishing execution
  • Confusing autocomplete suggestions that don’t reflect runtime behavior

Example or Code (if necessary and relevant)

A corrected structure looks like this:

# city.py
gray = (100, 100, 100)
darkgray = (50, 50, 50)

def draw_city(screen):
    import pygame
    pygame.draw.rect(screen, gray, (40, 500))
# main.py
import pygame
from city import draw_city, gray

pygame.init()
screen = pygame.display.set_mode((700, 500))
clock = pygame.time.Clock()

print(gray)

running = True
while running:
    for event in pygame.event.get():
        if event.type == pygame.QUIT:
            running = False

    draw_city(screen)
    pygame.display.flip()
    clock.tick(30)

pygame.quit()

How Senior Engineers Fix It

Experienced engineers avoid this class of bug by:

  • *Never using `import `**
  • Never putting Pygame drawing calls at module top level
  • Ensuring modules do not depend on each other’s runtime state
  • Passing dependencies explicitly (e.g., screen as a function argument)
  • Keeping modules pure—no side effects during import

Why Juniors Miss It

This issue is subtle because:

  • Autocomplete suggests variables even when they won’t exist at runtime
  • Wildcard imports hide the true source of names
  • Python’s import system silently executes code, which feels “invisible”
  • Pygame tutorials often show everything in one file, masking import‑order issues
  • Errors occur at runtime, not at import time, making debugging harder

The key takeaway: avoid wildcard imports, avoid top‑level Pygame calls, and structure modules so they don’t depend on each other’s initialization order.

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